Time Zones

I've had a problem with my website that's been troubling me for a couple of days now. It displays all times in UTC. What I want, though, is to tell it what time zone the user is in and have it convert the times to the correct time zone. This is easy enough with basic time zone info, but I also want to take daylight savings into account. So far, the only way I have found involves 11MB worth of timezone info and I'd rather not have to do this!

Does anyone know how I can provide a date and time along with a timezone name and automatically convert it to the correct time, including any daylight savings?

Any help would be much appreciated!